//
// Optimized for minimal code size.

#include "sha.h"

#include <stdio.h>
#include <string.h>

#define rol(bits, value) (((value) << (bits)) | ((value) >> (32 - (bits))))

static void SHA1_Transform(SHA_CTX* ctx) {
	uint32_t W[80];
	uint32_t A, B, C, D, E;
	uint8_t* p = ctx->buf;
	int t;

	for(t = 0; t < 16; ++t) {
		uint32_t tmp =  *p++ << 24;
		tmp |= *p++ << 16;
		tmp |= *p++ << 8;
		tmp |= *p++;
		W[t] = tmp;
	}

	for(; t < 80; t++) {
		W[t] = rol(1,W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16]);
	}

	A = ctx->state[0];
	B = ctx->state[1];
	C = ctx->state[2];
	D = ctx->state[3];
	E = ctx->state[4];

	for(t = 0; t < 80; t++) {
		uint32_t tmp = rol(5,A) + E + W[t];

		if (t < 20)
			tmp += (D^(B&(C^D))) + 0x5A827999;
		else if ( t < 40)
			tmp += (B^C^D) + 0x6ED9EBA1;
		else if ( t < 60)
			tmp += ((B&C)|(D&(B|C))) + 0x8F1BBCDC;
		else
			tmp += (B^C^D) + 0xCA62C1D6;

		E = D;
		D = C;
		C = rol(30,B);
		B = A;
		A = tmp;
	}

	ctx->state[0] += A;
	ctx->state[1] += B;
	ctx->state[2] += C;
	ctx->state[3] += D;
	ctx->state[4] += E;
}

static const HASH_VTAB SHA_VTAB = {
	SHA_init,
	SHA_update,
	SHA_final,
	SHA,
	SHA_DIGEST_SIZE
};

void SHA_init(SHA_CTX* ctx) {
	ctx->f = &SHA_VTAB;
	ctx->state[0] = 0x67452301;
	ctx->state[1] = 0xEFCDAB89;
	ctx->state[2] = 0x98BADCFE;
	ctx->state[3] = 0x10325476;
	ctx->state[4] = 0xC3D2E1F0;
	ctx->count = 0;
}


void SHA_update(SHA_CTX* ctx, const void* data, int len) {
	int i = ctx->count & 63;
	const uint8_t* p = (const uint8_t*)data;

	ctx->count += len;

	while (len--) {
		ctx->buf[i++] = *p++;
		if (i == 64) {
			SHA1_Transform(ctx);
			i = 0;
		}
	}
}


const uint8_t* SHA_final(SHA_CTX* ctx) {
	uint8_t *p = ctx->buf;
	uint64_t cnt = ctx->count * 8;
	int i;

	SHA_update(ctx, (uint8_t*)"\x80", 1);
	while ((ctx->count & 63) != 56) {
		SHA_update(ctx, (uint8_t*)"\0", 1);
	}
	for (i = 0; i < 8; ++i) {
		uint8_t tmp = cnt >> ((7 - i) * 8);
		SHA_update(ctx, &tmp, 1);
	}

	for (i = 0; i < 5; i++) {
		uint32_t tmp = ctx->state[i];
		*p++ = tmp >> 24;
		*p++ = tmp >> 16;
		*p++ = tmp >> 8;
		*p++ = tmp >> 0;
	}

	return ctx->buf;
}

/* Convenience function */
const uint8_t* SHA(const void* data, int len, uint8_t* digest) {
	SHA_CTX ctx;
	SHA_init(&ctx);
	SHA_update(&ctx, data, len);
	memcpy(digest, SHA_final(&ctx), SHA_DIGEST_SIZE);
	return digest;
}